This invention relates generally to apparatus for cleaning the doctor blades of a paper machine and, more particularly, to doctor blade cleaning apparatus which can operate in an automatic manner without interruption of the operation of the paper machine.
Paper making machines use a variety of different rolls for various functions during the paper making process. Thus, for example, press rolls, drying cylinders, and calender rolls are well known components of paper making machines. During the paper making process, various impurities adhere to the surface of the rolls which must be periodically cleaned. Doctor blades are conventionally utilized for cleaning these rolls.
A conventional doctor blade generally comprises the blade per se which extends in the cross-machine direction parallel to the axis of the roll being cleaned by it, the blade engaging the surface of the roll as the latter rotates. The blade is carried by a doctor blade beam which is usually attached to the frame of the paper making machine at bearing housings which are either specially provided or which constitute the bearing housings of the rolls. The pressure exerted by the doctor blade on the roll surface is usually selectively adjustable, such as by means of compressed air cylinders and, additionally, the doctor blades can generally oscillate.
As mentioned above, impurities such as paper fluff adhere to the paper machine rolls and are removed therefrom by the cleaning action of the doctor blades. Of course, the paper fluff and other impurities tend to stick to the doctor blades and, consequently, it is necessary to periodically clean the doctor blades. It is not uncommon for the doctor blades to be cleaned in a typical paper making machine at intervals of every one half to one hour. However, in order to clean conventional doctor blades, it is necessary to interrupt the operation of the paper making machine. More particularly, doctor blades are presently manually cleaned by means of brushes, scrapers and/or water jets. Since such manual operations require an extreme proximity of the cleaning personnel with the doctor blade and associated roller thereby rendering the work relatively dangerous, it is not possible to clean the doctor blades using presently known methods during operation of the paper making machine. Further, such manual cleaning procedures during machine operation would endanger the integrity of the web which, if obstructed, would most likely break if the paper making machine were operating.
Cleaning of the doctor blades is of particular importance in areas where it is possible to drive the broke downwardly through a defined space by means of gravity such, for example, at a smooth-surfaced stone roll, at the last cylinder of the drying section of the machine, and at the drying cylinders which precede the sizing press.
The use of conventional methods and apparatus for cleaning doctor blades necessarily requires cleaning intervals having a relatively long duration during which time the paper machine operation is interrupted. Such extended periods of interruption often result in difficulties arising in the operation of the paper making machine and, additionally, the quality of the paper produced correspondingly diminishes.